* Paul Walmsley <paul@xxxxxxxxx> [141113 15:01]: > Hi > > On Thu, 13 Nov 2014, Tony Lindgren wrote: > > > * Tomi Valkeinen <tomi.valkeinen@xxxxxx> [141113 03:33]: > > > On 12/11/14 17:02, Tony Lindgren wrote: > > > > > > >> And, with a quick grep, I see CONTROL_DEVCONF1 touched in multiple > > > >> places in the kernel. I wonder if adding a pinmux entry for it could > > > >> cause some rather odd problems. > > > > > > > > They can all use pinctrl-single no problem. > > > > > > Can, but don't. That's my worry. If we touch the DEVCONF1 via pinmux, > > > and we have code in mach-omap2 that also touch DEVCONF1, without any > > > knowledge (and locking) between those... > > > > Hmm yeah the McBSP clock mux could be racy as the mux register for > > McBSP is treated as a clock. This register muxes the clock between > > external pin and internal clock. Considering that this should be > > selectable at board level as the external clock probably needs to be > > used if level shifters are being used, it should be really handled by > > pinctrl-single. > > > > The other use for hsmmc.c and pdata-quirks.c for the one time mux for > > MMC clock from the MMC clock pin. That can be done with pinctrl-single > > from the MMC driver too for DT based booting. > > > > Then we just have the save and restore of the registers for > > off-idle. > > > > > So _maybe_ that's not an issue, as the pinmux config we have here is > > > fixed, and done once at boot time, and maybe the code in mach-omap2 that > > > touch DEVCONF1 is also ran just once and not at the same time as the > > > pinmux. But I don't know if that's so. > > > > It seems we could just do a read-only check for McBSP in the clock > > code for the mux register, or even completely drop that code from > > cclock3xxx_data.c and start using the pinctrl for that mux. > > > > Paul & Tero, got any comments here? > > It's best to move all of the SCM register reads/writes to an SCM IP block > driver. This driver would be the only entity that would touch the SCM IP > block registers - no other code on the system would touch it (perhaps > aside from anything needed for early init). The SCM driver would enforce > mutual exclusion via a spinlock, so concurrent SCM register modifications > wouldn't flake out. Then the SCM driver would register clocks with the > CCF, register pins with the pinctrl subsystem, etc. etc. We actually do have that with pinctrl-single + syscon. We certainly need to implement more Linux framework drivers for the SCM registers. Things like regulators, clocks, and PHYs, but they should use pinctrl-single + syscon. See the the pbias-regulator.c for example. Looking at the McBSP clock handling, threre's yet more handling of the same DEVCONF1 mux register in omap2_mcbsp_set_clks_src that gets alled from omap_mcbsp_dai_set_dai_sysclk. To me it seems that if we handle the DEVCONF with pinctrl-single, we don't need most of the McBSP fck code or the omap2_mcbsp_set_clks_src. Having the mux register as the clock enable register is not nice.. Who knows what the clock coming from the external pin might be :) Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
